The area where I see IQ failing miserably is in accounting for different types of intelligences. Like the parent commenter said, people solve the same problem differently. I'm keenly aware of this because I'm neurodivergent and I was continuously judged as poor in subjects that I liked the most and was very good at. I had to reformulate every problem and solution in a way that I understood (mostly based on spatial intelligence), leaving me at a significant disadvantage of time. And even then, those solutions were sometimes rejected, despite being objectively correct and clear in the dumbest possible way - just because it didn't follow the textbook pattern. That continued until we were in a situation where we had to solve the problems ourselves.

The reason I mention this is because I see the exact same problem with IQ tests. It emphasizes certain types of intelligences and ignores others. Human intelligence is extremely multidimensional and a single number is simply incapable of representing its overall quality. For example, there are people who score poorly in IQ, but are superhuman in remembering places and navigating their way around complex routes. Meanwhile, many high scoring ones become hopelessly lost, failing to institute or follow even simple mitigation strategies for that problem. There are situations where this determines whether you live or die, and your IQ score becomes worthless indicator of even your survival.

Afaik iq correlates highly with g-factor (scientific name for general intelligence). We don't have much better ways to measure it.

Overall, afaik, again, problem solving often needed in our society correlates with this: "general intelligence". When people say: "But there are many ways to approach a problem, many types of intelligence".

This very well may be, but data consistently shows that people having high IQ scores solve different problems better. So, contrary to popular belief, people having higher iq in general have better talent for languages, same with understanding others emotions and using it to your advantage ("emotional intelligence").

As for reframing an issue and solving it in a different way. This may be valid approach (to teach people etc). But IQ is also time-measured. If your new approach does not help you to solve previously unseen problems quickly, it is not noticably increase your intelligence.

Thus, we see consistently that people cannot really prepare for iq tests much. You only get a few points more if you prepare. Same difference as if you are sleep-deprived.